netdev - Re: [PATCH v2 1/4] tcp: md5: Fix overlap between vrf and non-vrf keys

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Date:   Wed, 13 Oct 2021 21:05:39 -0600
From:   David Ahern <dsahern@...il.com>
To:     Leonard Crestez <cdleonard@...il.com>,
        David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Kuniyuki Iwashima <kuniyu@...zon.co.jp>,
        Yonghong Song <yhs@...com>,
        Alexander Duyck <alexanderduyck@...com>,
        Florian Westphal <fw@...len.de>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] tcp: md5: Fix overlap between vrf and non-vrf keys

On 10/13/21 12:50 AM, Leonard Crestez wrote:
> With net.ipv4.tcp_l3mdev_accept=1 it is possible for a listen socket to
> accept connection from the same client address in different VRFs. It is
> also possible to set different MD5 keys for these clients which differ
> only in the tcpm_l3index field.
> 
> This appears to work when distinguishing between different VRFs but not
> between non-VRF and VRF connections. In particular:
> 
>  * tcp_md5_do_lookup_exact will match a non-vrf key against a vrf key.
> This means that adding a key with l3index != 0 after a key with l3index
> == 0 will cause the earlier key to be deleted. Both keys can be present
> if the non-vrf key is added later.
>  * _tcp_md5_do_lookup can match a non-vrf key before a vrf key. This
> casues failures if the passwords differ.
> 
> Fix this by making tcp_md5_do_lookup_exact perform an actual exact
> comparison on l3index and by making  __tcp_md5_do_lookup perfer
> vrf-bound keys above other considerations like prefixlen.
> 
> Fixes: dea53bb80e07 ("tcp: Add l3index to tcp_md5sig_key and md5 functions")
> Signed-off-by: Leonard Crestez <cdleonard@...il.com>
> ---
>  net/ipv4/tcp_ipv4.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 

Reviewed-by: David Ahern <dsahern@...nel.org>